1. Field of the Invention
The present invention is generally directed to a surface covering product. More specifically, the present invention is directed to a floor covering product having a precoated film wearlayer in which the gloss level of the coating is controlled.
2. Description of the Related Art
Surface covering products, such as floor tiles and floor covering sheets, are well known in the art. The xe2x80x9cgloss,xe2x80x9d or shine, of the floor covering product is commercially significant since differing gloss levels in floor covering products are desired by the consumer. Accordingly, it is known that gloss control can be accomplished through various processes, including by altering the specific coating composition for the amount of gloss desired on the end product, and by controlling the curing of the coating.
A floor covering sheet is frequently manufactured on a belt or drum line, where a substrate is laminated with a transparent covering, or xe2x80x9cwearlayer,xe2x80x9d such that the end product can withstand foot traffic. The wearlayer may be embossed, and if embossed the embossing is done simultaneously with or after the lamination. The wearlayer can be a coated or uncoated film such as a rigid film comprised of polyvinyl chloride (PVC), polyethyleneterephthalate (PET), or glycolated polyethyleneterephthalate (PETG). xe2x80x9cRigid filmxe2x80x9d is a term of art which means any film that is substantially free of plasticizers, e.g. phthalate esters, thereby imparting resistance of the polymer to deform. Other floor products are coated or covered with the wearlayer, which is typically comprised of a curable composition, such as acrylated urethane or acrylated polyethylene, and is coated in liquid or flowable form onto a vinyl or nonvinyl composition substrate. The wearlayer typically is then cured to form the durable covering to withstand repeated contact in use.
U.S. Pat. No. 4,313,969 to Matthews shows a prior method and apparatus for providing low gloss and gloss controlled radiation cured coating. Matthews discloses a filtered mercury bulb to control spectral distributions. Thus, the gloss control is particularly achieved by varying spectral distribution in curing the coating, and Matthews generally describes gloss control therefrom.
It also is known to cure the wearlayer by controlled exposure to ultraviolet radiation from commercially available mercury lamps. The mercury lamps, however, have a significant infrared component, which conveys excess heat to the curing substrate. If the wearlayer is coated on a rigid vinyl film and cured, excess heat causes a problem when the glass transition temperature of the vinyl film is exceeded. The excess heat causes distortion of the film and results in an unaesthetic appearance of the resultant floor covering product.
The present invention is a composition and method for manufacturing a surface covering, particularly a covering product, comprised of a controlled gloss composition that is coated on a rigid film to form a wearlayer. The coated rigid film is prepared by the use of low intensity UV energy followed by exposure to low energy electron beam radiation that is controlled to avoid yellowing the decorative rigid film by degradation processes commonly observed for PVC film. The preferred composition contains a conventional flatting agent to lower gloss, and also contains hard inorganic particulates, such as aluminum oxide particles, to improve abrasion resistance of the exposed surface of the wearlayer. The composite structure is laminated to a substrate under known process conditions that preferably result in an aesthetically acceptable floor covering.
In the preferred process of making the surface covering, the low gloss wearlayer composition is formed by the reaction of a hydroxyterminated polyester with an isocyanurate in the presence of multifunctional acrylates and hard particles. Partial polymerization is catalyzed by low intensity UV radiation to gel (i.e. partially cure) the wearlayer surface to form a low gloss coating. The final polymerization is catalyzed either from exposure to low energy electron beam radiation or to high intensity UV radiation. Alternatively, a cured coated decorative film is laminated to a substrate, which may be cut to form a floor tile product of desired dimensions.
Therefore, it is an object of the present invention to provide a process of selectively producing either a high, medium and/or low gloss floor coating from the same composition which is coated on a substrate. The present invention also includes the various products produced by this process. In the preferred embodiment, gloss levels can be controlled by varying UV radiation intensity. The intensity of the initial UV exposure can be changed by various known means, including but not limited to varying the distance between the lamp head and substrate and/or by changing input power of the source.
It is a further object of the present invention to provide a flexible process to prepare variable gloss level wearlayers on PVC film. In the preferred embodiment, the acrylated urethane coating is partially cured to a xe2x80x98gel statexe2x80x99 using low intensity UV radiation while the film is in contact with a temperature controlled drum. Using this process, the low intensity UV radiation does not cause distortion of the PVC film by shrinkage processes commonly observed when PVC film is exposed to heat above its distortion temperature.
It is a further object of the present invention to provide a process to prepare high, medium and low gloss floor wearlayer surfaces from the UV-cured coating compositions on the surface covering product. For example, UV-cured resin materials having a high viscosity typically will not form a low gloss surface upon exposure to UV, due to a lack of mobility of the flatting agent to the surface. Thus, in the preferred embodiment, the viscosity of the resin material is controlled prior to xe2x80x98partial gelationxe2x80x99 by use of a heated drum. Gloss control further can be achieved by varying the temperature of the drum prior to initial exposure to UV radiation.
Other objects, features and advantages will become apparent after review of the hereinafter set forth Brief Description of the Drawings, Detailed Description of the Invention and Claims appended herewith.